A technology is known that stacks a graphene with an organic molecular film and dopes the graphene with electrons or holes by the organic molecular film to reduce the sheet resistance of the graphene. In addition, a technology is known that uses a graphene in a transistor. For example, a gas sensor has been proposed which uses a graphene as a gate of a field effect transistor (FET) and detects a target gas based on a change in the drain current caused by a change in the threshold voltage due to a change in the work function when the target gas such as, for example, ammonia is adsorbed onto the graphene.
Related techniques are disclosed in, for example, International Publication Pamphlet Nos. WO 2014/030534 and WO 2017/002854.